JPH11289324A - Transmitter-receiver and transmission-reception method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the confidentiality an IC card and IC card system, using an enciphering method of a common key, a public key and a secret key. SOLUTION: A public key register 115 is transferred to another party, an another party public key register 117 on the transmission side and the public key register 115 on the reception side are stored in the second common key generation register, a common key 108 is generated from the first common key generation value register 103 and the second common key generation value register 104 on the basis of common key generation information 106, the common key generation information 106 is transferred to the other party, and a common key whose value is shared by the other party is generated. It becomes possible to improve the confidentiality of an IC card 100 and an IC card system using the IC card 100, by making the common key 108 a key of a common key ciphering system and performing enciphering through combining it with the public key ciphering system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a secret key, a public key,
The present invention relates to a transmission / reception device and a transmission / reception method using a secret key.

[0002]

2. Description of the Related Art FIG. 6 shows an internal block diagram of a transmitting side IC card in a conventional transmitting / receiving apparatus using a common key cryptosystem and a public key cryptosystem. The internal structure of the receiving IC card is the same as that of the transmitting IC card.

In FIG. 6, an IC card 600 has an input / output terminal 601 for inputting / outputting data to / from a partner IC card which performs transmission / reception. The CPU 602 controls the inside of the IC card 600. The random number generation unit 603
The CPU 602 generates a random number to be transferred to the C card, and
Transfer to The other party's random number register 604 stores the random number sent from the other party's IC card. The common key register 605 stores a common key in the common key cryptosystem.
The common key has the same value on the transmitting and receiving IC cards. The common key encryption processing unit 606 encrypts the other party random number stored in the other party random number register 604 by using the common key stored in the common key 605 as a key, generates the data 607, and generates the data 608. Is decoded to generate data 609. The public key register 610 stores a public key used for a public key cryptosystem. The secret key register 611 stores a secret key used for the public key cryptosystem. The partner public key register 612 stores the public key of the partner IC card transferred from the partner IC card.
The public key encryption processing unit 613 generates data 614 by encrypting the data 607 using the other party's public key stored in the other party's public key register 612 as a key, and transfers the data 614 from the other party's IC card. The data 615 is decoded to generate data 608.

[0004] Next, FIG. 7 shows a mutual authentication operation between a transmitting IC card and a receiving IC card by a conventional encryption method using a public key encryption method and a common key encryption method. In addition,
CKE and CKD are respectively encrypted and decrypted by the common key encryption method performed by the common key encryption processing unit 606, PKE and PKD
Represents encryption and decryption by the public key encryption method performed by the public key encryption processing unit 613, respectively.

[0005] In FIG. 7, the mutual authentication method between the sending IC card 700 and the receiving IC card 701 is described in STEP.
This is shown in steps 71 to 74. Here, the data transmission side IC card 700 includes a public key D, a secret key D,
It has a random number D and a common key. The data receiving side IC card 701 has a public key E, a secret key E, a random number E, and a public key. The internal structure of the transmitting IC card 700 is the same as that of the receiving IC card 701, and the same operation as described below is performed even if the transmitting and receiving IC cards are switched. Hereinafter, description will be made for each step.

STEP 71: IC card 700 on the transmitting side
Transfers the random number D and the public key D to the receiving-side IC card 701.

STEP72: Receiving IC card 701
Encrypts a random number D with a common key using a common key as a key to generate data SD0, encrypts the data SD0 with a public key D as a key using a public key encryption method, and generates data SD0.
D1 is generated. Then, the data SD1, the public key E, and the random number E are transferred to the transmission-side IC card 700.

STEP 73: IC card 700 on the transmitting side
Decrypts the data SD1 by the public key cryptosystem using the secret key D as a key to generate data SD2,
Is decrypted using a common key as a key by a common key cryptosystem to generate data SD3. Then, SD3 is compared with the random number D, and if they match, the receiving side IC card 701
Is authenticated, and if they do not match, an authentication error occurs. If the authentication is successful, the random number E is encrypted using a common key as a key by using a common key encryption method to generate data SD4, and the data SD4 is encrypted using a public key E as a key using a public key encryption method and the data SD5 is encrypted. Generate. Then, the data S
D5 is transferred to the receiving-side IC card 701.

STEP 74: Receiving IC card 701
Decrypts the data SD5 by the public key cryptosystem using the secret key E as a key to generate data SD6,
Is decrypted using a common key as a key by a common key encryption method,
The data SD7 is generated. Then, the SD 7 and the random number E are compared, and if they match, the sender IC card 700 is authenticated to complete the mutual authentication. If they do not match, an authentication error occurs.

[0010]

However, in the above-mentioned conventional transmitting / receiving apparatus and method using a common key, a public key, and a secret key, the common key, the public key, and the secret key are fixed. Becomes public, the data transfer between the sending IC card and the receiving IC card by the encryption method using those keys will not be meaningful from next time.
There is a problem that the confidentiality of the card and the IC card system is low.

[0011]

According to an aspect of the present invention, there is provided a transmitting / receiving apparatus for generating a common key and a common key generation value for generating a common key. Receiving common key generation information indicating a generation method, generating a common key from the common key generation value based on the common key generation information, and transmitting the received common key generation value and common key generation information. is there.

With the above configuration, the content of the common key cannot be known only by the generation information of the common key transferred between the transmitting and receiving apparatuses, so that the transmitting and receiving apparatus using the common key can increase the confidentiality of transmission and reception. Becomes

[0013] In order to solve the above-mentioned problem, a transmitting and receiving apparatus according to a second aspect of the present invention has a first common key generation value for generating a common key, and has a first common key generation value for generating a common key. 2 and a common key generation information indicating a generation method for generating a common key, and generating a common key from the first and second common key generation values based on the common key generation information. And transmits the received second common key generation value and common key generation information.

According to the above configuration, the number of combinations of common keys can be increased, so that transmission / reception confidentiality can be enhanced in a transmission / reception apparatus using the common keys.

According to a third aspect of the present invention, there is provided a transmitting / receiving apparatus according to the third aspect of the present invention, wherein the received common key generation information is replaced with the second common key generation information. And a function of transmitting the second common key generation information.

According to the above configuration, in addition to the effects of the first and second aspects of the present invention, the number of combinations of common keys can be further increased. It is possible to increase.

According to a fourth aspect of the present invention, there is provided a transmission / reception apparatus according to the fourth aspect, wherein the second common key generation information is set to a different value within a predetermined time. It is to be.

According to the above configuration, in addition to the effect of the third aspect of the present invention, the same common key is not used within a predetermined time. Can be increased.

In order to solve the above problem, a transmitting / receiving apparatus according to a fifth aspect of the present invention has a function of updating a public key.

According to the above configuration, since the public key is not fixed to one value, it is possible to increase the confidentiality of transmission and reception in the transmitting and receiving apparatus using the public key.

According to a sixth aspect of the present invention, there is provided a transmission / reception apparatus according to the sixth aspect of the present invention, wherein the updated public key is replaced with a secret key after updating the public key. Things.

According to the above configuration, in addition to the effect of the invention described in claim 5, since the public key and the secret key are not fixed to one value, the transmitting and receiving apparatus using the public key and the secret key Confidentiality in transmission and reception can be increased.

According to a seventh aspect of the present invention, there is provided a transmitting / receiving apparatus for encrypting information about a common key at least once with a public key, and for transmitting a public key at least once with a common key. It has an encryption function.

According to the above configuration, the confidentiality of the common key and the public key can be enhanced, so that the transmitting and receiving apparatus using those keys can enhance the confidentiality of transmission and reception.

In order to solve the above-mentioned problem, a transmitting / receiving method according to the invention of claim 8 is characterized in that:
The first transmitting / receiving device transmits the first public key to the second transmitting / receiving device, and the second transmitting / receiving device generates first common key generation information for generating a common key, based on the first common key generation information. Generating a first common key from the received first public key and the first common key generation value, encrypting the first common key generation information using the received first public key as a key, Generating first encrypted data, encrypting a second public key using the first common key as a key to generate second encrypted data, and transmitting the second encrypted data to the received first encrypted data; Encrypted with the public key of the third
, And transfers the first and third encrypted data to the first transmitting / receiving apparatus. The first transmitting / receiving apparatus uses the secret key corresponding to the first public key as a key to generate the first and third encrypted data. 1 to generate first decryption data, and the first decryption data is used as a key to generate the first decryption data.
Generating a second common key having the same value as the first common key from the public key and the second common key generation value having the same value as the first common key generation value; Decrypting the transferred third encrypted data to generate second decrypted data, and using the second common key as a key,
Has a function of decrypting the decrypted data to generate a third public key equal to the second public key.

With the above configuration, the confidentiality of the public key can be increased. Therefore, by using a transmission / reception method using the public key, the confidentiality of transmission / reception can be increased.

[0027] In order to solve the above problem, according to a ninth aspect of the present invention, a first transmitting / receiving apparatus generates first common key generation information for generating a common key,
Generating a first common key from first and second common key generation values based on the first common key information, transmitting the first common key generation information to a second transmitting / receiving device, 2 transmitting / receiving apparatus, based on the received first common key generation information,
And generating a second common key having the same value as the first common key from the third and fourth common key generation values having the same value as the second common key generation value, respectively. The apparatus generates second common key generation information, generates a third common key from the third and fourth common key generation values based on the second common key generation information, and generates the second common key generation information. Overwriting a common key and transmitting the second common key generation information to the first transmitting / receiving apparatus, wherein the first transmitting / receiving apparatus
Generates a fourth common key having the same value as the third common key from the first and second common key generation values based on the common key generation information, and overwrites the first common key. It has a function.

With the above configuration, the confidentiality of the common key can be increased. Therefore, by using a transmission / reception method using the common key, the confidentiality of transmission / reception can be increased.

[0029] In order to solve the above-mentioned problems, the transmitting and receiving method according to the invention described in claim 10 is based on claims 8 and 9.
In the transmission / reception method described above, the first transmission / reception device includes:
Encrypts the authentication data to generate first encrypted data, transmits the first encrypted data to a second transmitting / receiving device, and the second transmitting / receiving device transmits the received first encrypted data to the second transmitting / receiving device. Decrypting the data to generate first decrypted data, and if the first decrypted data is equal to the value of the second authentication data having the same value as the first authentication data, the first authentication is performed. The third authentication data is encrypted and the second
, And transmits the second encrypted data to the first transmitting / receiving apparatus, and the first transmitting / receiving apparatus decrypts the received second encrypted data to perform a second decryption. Encrypted data, and if the value of the second decryption data is equal to the value of the fourth authentication data having the same value as the third authentication data, it is determined that the second authentication has been established, and the first and second authentication data are determined. It has a function of performing mutual authentication when the second authentication is established.

[0030] With the above configuration, the confidentiality of data used for mutual authentication can be enhanced by using the effects of the inventions of claims 8 and 9. Therefore, the transmission and reception method using the authentication method can be used. Thus, the confidentiality of transmission and reception can be increased.

[0031]

Embodiments according to the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a block diagram according to Embodiment 1 of the present invention. In FIG. 1, the IC
The card 100 includes an input / output terminal 101 for inputting / outputting data to / from a partner IC card that performs transmission / reception. C
The PU 102 controls the inside of the IC card 100. The first common key generation value register 103 stores the first data of two data required to generate a common key. The second common key generation value register 104 stores the second data of the two data required to generate the common key. Common key generation information register 105
Stores common key generation information 106 which is data indicating how to generate a common key from the values of the first and second common key generation value registers. The common key generation unit 107 generates a common key 108 from the first common key generation value register 103, the second common key generation value register 104, and the common key generation information 106. The common key memory 109 stores a common key for a predetermined period in the past, and the CPU 102 manages common key generation information to be generated so that the same common key is not generated during that period. The common key cryptographic processing unit 111 encrypts the data 110 using the common key 108 as a key to generate data 112,
Is decrypted to generate data 114. The public key register 115 stores a public key used for the public key cryptosystem. The secret key register 116 stores a secret key used for the public key cryptosystem. The other party's public key register 117 stores the other party's IC
Stores the other party's public key transferred from the card. The public key processing unit 119 uses the other party's public key 118 as a key and generates the common key generation information 106 and the data 11
2 to generate data 120, and
21 is decrypted to generate data 113.

FIG. 2 shows an internal block diagram of the common key generation unit 107. The first bit exchange circuit 200 uses the common key generation information 106 to generate the first common key generation register 10.
The first data 201 is generated by exchanging the 3 bits. Similarly, the second bit exchange circuit 202 uses the common key generation information 106 to generate the second common key generation register 1
The second data 203 is generated by exchanging the bits of “04”. The exclusive OR generation circuit 204 generates the first data 20
An exclusive OR of the 1 and the second data 203 is generated for each bit, and a common key 108 is generated.

FIG. 3 shows a mutual authentication procedure according to the first embodiment of the present invention. Here, in a certain number of times of mutual authentication, the transmission-side IC card 300 determines the public key A, the secret key A, the first common key generation value, and the second common key generation value of the partner public key register 117 as the second common key generation value. It is assumed that the common key generation information A has a value, that is, a public key B which is a public key of the other party, and the common key generation information A is generated as the common key generation information. In the mutual authentication, the receiving side IC card 301 uses the public key B, the secret key B, the first common key generation value, the public key B as the second common key generation value, and the common key generation information as the common key generation information. It is assumed that key generation information B is generated. Based on the above settings, the procedure of mutual authentication will be described according to STEP31 to STEP35. CKE and CKD are the common key cryptographic processing unit 1 respectively.
11, encryption and decryption by common key encryption, PK
E and PKD represent encryption and decryption by the public key cryptosystem performed by the public key cryptographic processor 119, and CKM represents a common key generation process performed by the common key generator 107.

STEP31: Receiving IC card 301
Transfers the public key B to the sending IC card 300.

STEP32: IC card 300 on the transmitting side
Generates the common key A from the first common key generation value and the public key B using the common key generation information A. Also, the common key generation information A
Is encrypted by the public key cryptosystem using the public key B as a key to generate data TD0. Further, the public key A is encrypted by the common key
D1 is generated, and the data TD1 is encrypted by the public key cryptosystem using the public key B as a key to generate data TD2.
Then, the data TD0 and the data TD2 are transferred to the receiving-side IC card 301.

STEP33: Receiving IC card 301
Decrypts the data TD0 by the public key cryptosystem using the secret key B as a key, and generates the common key generation information A. Then, a common key A is generated from the first common key generation value and the public key B using the common key generation information A. In addition, the data TD2 is decrypted by using the secret key B as a key by a public key cryptosystem to generate data TD3, and the data TD3 is decrypted by a common key A using a common key A to generate a public key A.
Then, the common key generation information A is updated to the common key generation information B, and the common key B is generated from the first common key generation value and the public key B based on the common key generation information B. Also, common key generation information B
Is encrypted by the public key cryptosystem using the public key A as a key to generate data TD5. Also, the data TD3 is encrypted by using the common key B as a key by a common key encryption method to generate data TD6, and the data TD6 is encrypted by a public key A using a public key A as a key to generate data TD7. Then, the data TD5 and the data TD7 are transmitted to the transmitting side IC.
Transfer to the card 301.

STEP 34: IC card 300 on the transmitting side
Decrypts the data TD5 by using a secret key A as a key by a common key encryption method to generate common key generation information B, and updates the common key generation information A held up to that time to the common key generation information B. Then, a common key B is generated from the first common key generation value and the public key B using the common key generation information B. Further, the data TD7 is decrypted by using the secret key A as a key by a public key encryption method to generate data TD8, and the data TD8 is decrypted by using a common key B as a key by a common key encryption method and the data T
Generate D9. Then, data TD9 and data TD1
And if they match, the receiving IC card 30
Authenticate 1. If they do not match, an authentication error occurs. If they match, the data TD8 is encrypted with the common key B using the common key B as a key to generate data TD10, and the data TD10 is converted into the common key B using the common key encryption method.
Is used as a key to generate data TD11. Then, the data TD11 is transferred to the receiving-side IC card 301.

STEP35: Receiving IC card 301
Generates the data TD12 by decrypting the data TD11 using the secret key B as a key by the public key cryptosystem, and generates the data TD12.
The data TD13 is generated by decrypting D12 using the common key B as a key according to the common key cryptosystem. And the data TD
13 is compared with the data TD6, and if they match, the transmitting side IC card 300 is authenticated.

With the above configuration, the confidentiality of the common key, public key, and secret key of the IC card is increased for the following reasons (1) and (2). The confidentiality of the IC card system can be improved.

1. The possibility that the common key, the public key, or the secret key becomes public is reduced. The common key is generated inside the IC card, and information for generating the common key is transferred instead of transferring the common key itself so that the partner IC card owns the same common key. Similarly, since the common key is generated inside the side IC card, the common key cannot be derived unless the internal structure of the IC card is known. Therefore, the possibility that the common key becomes public is reduced.

Further, since the public key of the transmitting side IC card is encrypted and transferred using the common key as a key, the possibility of publicizing the public key is reduced. Since the possibility that the public key becomes public becomes low, the possibility that the secret key in the encryption / decryption relationship becomes public becomes low.

2. Even if the common key becomes public, the common key is updated. Even if the common key becomes public, the common key is updated each time it is used as a key until the first authentication in mutual authentication. Can not be done.

Further, the IC card has a memory for storing the history of the common key. In order to prevent the use of the common key having the same value during the period of the history, the public key immediately becomes public. And it is more confidential.

In the above description, the common key generation unit
Although the configuration is made up of the bit replacement circuit and the exclusive OR generation circuit, any circuit that can perform a logical OR circuit or an AND circuit may be used as long as a bit operation can be performed. In addition, any operation may be used instead of the bit operation as long as one data can be reversibly operated from two data in accordance with a certain rule.

In the above description, a configuration is described in which two common key generation values are used to generate a common key.
A configuration in which a common key generation value is set to one and a common key generation value is generated by performing a bit operation and a bit operation on one common key generation value is also possible.

The common key generation information may be updated each time the common key is used. (Embodiment 2) Embodiment 2 shows an embodiment of the present invention in which a public key and a secret key can be updated in addition to the operations described in Embodiment 1.

FIG. 4A shows a connection between the IC card 400 and the public key / private key updating apparatus 401 according to the second embodiment of the present invention when the public / private key is updated. IC card 400 is the main body of the IC card of the present embodiment.
The public key / private key update device 401 is a device for updating the public key and the secret key of the IC card 400. A common key cryptosystem is used to transfer the cryptographic data.

FIG. 4B shows a block diagram of the IC card 400. In the figure, reference numerals 101 to 114, 11
Reference numerals 7 to 121 correspond to the same reference numerals shown in FIG. 1 as the first embodiment. The special code 402 is
The IC card 400 is used to authenticate the public key private key update device 401, and the authentication is established when the public IC card 400 can confirm that the open key private key update device 401 also has the special code. The value of the first common key generation value register 104 is used as the common key. Therefore, the second
Of the common key generation register 103 is reset to 0, and a signal is output to the common key generation information 105 so that the bit of the first common key generation value register is output as it is. The public key register 403 and the secret key register 40
4 are both configured as writable and readable registers.

FIG. 5 shows a procedure for updating the secret key and the public key in FIG. Hereafter, step 5
1 and 52 will be described. Note that CKE and CKD represent encryption and decryption by the common key encryption method performed by the common key encryption processing unit 111, respectively.

STEP 51: Public key / private key updating apparatus 50
1 generates a data RW0 by encrypting a specific code by a common key cryptosystem using a first common key generation value as a key.
Also, the data RW1 is generated by encrypting the public key C by a common key cryptosystem using the first common key generation value as a key. Then, the data RW0 and RW1 are transmitted to the transmitting side IC card 500.
Transfer to

STEP 52: IC card 500 on the transmitting side
Decrypts data RW0 by a common key cryptosystem using the first common key generation value as a key to generate data RW2.
Then, RW2 is compared with the specific code, and if they match, authentication is established, and if they do not match, an authentication error is determined. If they match, the data RW1 is decrypted by a common key cryptosystem using the first common key generation value as a key to generate a public key C, and the public key A is updated to the public key C. Further, the public key C and the secret key A are exchanged. The public key and the private key are updated as described above.

With the above configuration, the public key and the secret key are updated after a predetermined period, so that they can be kept secret even if they become public. By using IC cards and ICs
The confidentiality of the card system can be increased.

[0054]

As described above, according to the present invention, a common key, a public key,
Since the confidentiality of the secret keys is increased, it is possible to increase the confidentiality of transmission and reception in the transmitting and receiving apparatus and the transmitting and receiving method using those keys.

1. The possibility that the common key, the public key, or the secret key becomes public is reduced. The common key is generated inside the transmitting / receiving device, and information for generating the common key is transmitted instead of transferring the common key itself so that the other transmitting / receiving device has the same common key. Similarly, a common key is generated inside the transmitting / receiving apparatus. Since the common key cannot be derived unless the internal structure of the transmitting / receiving apparatus is known, the possibility that the common key becomes public is reduced.

Further, since the public key of the transmitting / receiving device is encrypted and transferred using the common key as a key, the possibility of publicizing the public key is reduced. Since the possibility that the public key becomes public becomes low, the possibility that the secret key in the encryption / decryption relationship becomes public becomes low.

2. Even if the common key, the public key, and the secret key become public, those keys are updated. Even if the common key becomes known, the common key is updated each time it is used as a key until or every time the first authentication in mutual authentication is performed. Decryption cannot be performed. Further, the transmitting and receiving apparatus has a memory for storing the history of the common key, and in order to use the common key having a different value during the period of the history, the public key that has become publicly known is repeatedly used immediately. Without
This further increases confidentiality. Further, the public key and the secret key can be updated as needed.

[Brief description of the drawings]

FIG. 1 is a block diagram of an IC card according to an embodiment of the present invention.

FIG. 2 is a block diagram of a common key generation unit of the IC card according to the embodiment of the present invention;

FIG. 3 is a protocol diagram according to an embodiment of the present invention.

4A is a diagram showing a connection for updating a public key private key, and FIG. 4B is a block diagram of an IC card capable of updating a public key and a secret key according to an embodiment of the present invention.

FIG. 5 is a protocol diagram for updating a public key and a secret key.

FIG. 6 is a block diagram of a conventional IC card.

FIG. 7 is a protocol diagram of a conventional IC card.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 IC card main body 101 input / output terminal 102 CPU 103 first common key generation value register 104 second common key generation value register 105 common key generation information register 106 common key generation information 107 common key generation unit 108 common key 109 common key Memory 111 Common key encryption processing unit 115 Public key register 116 Private key register 117 Other party public key register 119 Public key encryption processing unit 402 Specific code

──────────────────────────────────────────────────続 き Continuation of front page (51) Int.Cl. ⁶ Identification code FI G06K 19/10 G06F 15/30 340 G09C 1/00 660 G06K 19/00 R H04L 9/00 601E

Claims (10)

[Claims] 1. A common key generation value for generating a common key,
Receiving common key generation information indicating a generation method for generating a common key; generating a common key from the common key generation value based on the common key generation information; A transmission / reception device for transmitting generation information. 2. A method for generating a common key, comprising a first common key generation value for generating a common key, a second common key generation value for generating a common key, and a generation method for generating a common key. Receiving common key generation information, generating a common key from the first and second common key generation values based on the common key generation information, and receiving the received second common key generation value and common key generation information; A transmission / reception device, which transmits: 3. The transmitting / receiving apparatus according to claim 1, further comprising a function of updating the received common key generation information to second common key generation information and transmitting the second common key generation information. A transmitting / receiving device characterized by the above-mentioned. 4. The transmitting / receiving apparatus according to claim 3, wherein
A function of setting the common key generation information to different values within a predetermined time. 5. A transmitting / receiving device having a function of updating a public key. 6. The transmitting / receiving apparatus according to claim 5, wherein after updating the public key, the updated public key is replaced with a secret key. 7. A transmitting / receiving apparatus having a function of encrypting information about a common key at least once with a public key and a function of encrypting a public key at least once with a common key. 8. A first transmitting / receiving device transmits a first public key to a second transmitting / receiving device, and the second transmitting / receiving device generates first common key generation information for generating a common key. , The first
Generating a first common key from the received first public key and the first common key generation value based on the common key generation information of the first key, and using the received first public key as a key to generate the first common key. Encrypting the common key generation information to generate first encrypted data;
Encrypts the second public key using the common key of the second key as a key to generate second encrypted data, encrypts the second encrypted data with the received first public key, and encrypts the third encrypted data. Generating and transferring the first and third encrypted data to the first transmitting / receiving device, wherein the first transmitting / receiving device performs the first encryption using a secret key corresponding to the first public key as a key. Decrypting the data to generate first decrypted data;
And the first public key and the first
A second common key having the same value as the first common key is generated from a second common key generation value having the same value as the common key generation value of the third key, and the transferred third key is used as the secret key as a key. To generate second decrypted data, decrypt the second decrypted data using the second common key as a key, and obtain a third public key equal to the second public key. A transmission / reception method having a function of generating a key. 9. A first transmission / reception device generates first common key generation information for generating a common key, and generates first and second common key generation values based on the first common key information. And generates a first common key from the first transmission key, transmits the first common key generation information to a second transmission / reception apparatus, and the second transmission / reception apparatus transmits the received first
From the third and fourth common key generation values having the same values as the first and second common key generation values, respectively, based on the common key generation information The second transmission / reception device generates second common key generation information, and generates the second common key generation information from the third and fourth common key generation values based on the second common key generation information. 3 and overwrites the second common key, overwrites the second common key, transmits the second common key generation information to the first transmitting / receiving device,
The transmission / reception device of the third of the third from the first and second common key generation value based on the received second common key generation information
A function of generating a fourth common key having the same value as the common key and overwriting the first common key. 10. The transmission / reception method according to claim 8, wherein the first transmission / reception device encrypts the first authentication data to generate first encrypted data, and generates the first encrypted data. The first transmission / reception device transmits the first encrypted data to the second transmission / reception device to generate the first decryption data by decrypting the received first encrypted data. If the values of the second authentication data having the same value as the first authentication data are equal, the first authentication is established,
Generates the second encrypted data by encrypting the authentication data, transmits the second encrypted data to the first transmitting / receiving apparatus, and the first transmitting / receiving apparatus transmits the received second encrypted data. Decrypting the data to generate second decrypted data;
If the values of the second decryption data and the fourth authentication data having the same value as the third authentication data are equal, it is determined that the second authentication has been established, and the first and second authentications have been established. A transmission / reception method characterized in that the transmission / reception method has a function of performing mutual authentication.